This invention relates to a light-sensitive silver halide phtographic material which is improved in photographic properties, more particularly to a light-sensitive silver halide photographic material in which the occurence of a photographic fog is restrained and a high sensitization has been achieved.
In recent years, requirements for the light-sensitive silver halide photographic mateiral (hereinafter referred simply to as the light-sensitive material) has been getting strict increasingly, and particularly, the light-sensitive meterial having high sensitivity and excellent image characteristics has increasingly been desired.
For the purpose of improving an image quality of the high-sensitivity light-sensitive silver halide photographic material, a variety of techniques has heretofore been developed. For example, one well known technique, by which image qualities such as gradation, graininess and sharpness are improved, comprises adding silver iodide to a silver halide composition, especially silver halide grains in order to utilize a development inhibition effect by virtue of iodine ions given off at the time of development.
For example, the silver halide emulsion used as the light-sensitive silver halide material for black and white photography generally contains 2 mole % or more of silver iodide; therefore this emulsion can be utilized in the above-mentioned technique with the intention of regulating the image qualities. Further, in particular, the light-sensitive silver halide material for color photograpy generally contains 4 mole % or more silver iodide. Thus the aforesaid technique can be utilized more effectively in the presence of this material. Such a high content of silver iodide is suitable for the improvement in the image qualities but it is not always preferred for the betterment of sensitivity, because the silver iodide acts to inhibit a sulfur sensitization reaction during a chemical ripening or a development reaction during a chemical ripening.
A desensitization resulting from the above inhibitive action at the chemical ripening or development can be fairly recovered, for example, by adding a greater amount of a sulfur sensitizer, a gold sensitizer or the like to the emulsion at the chemical ripening, but this disadvantageously deteriorates stability with time for the emulsion solution, the light-sensitive material and the like.
On the other hand, in a color light-sensitive material, a silver halide emulsion layer has, in general, spectrally sensitized in each of red, green or blue light-sensitive region. In case where the silver halide emulsion layer is subjected to spectral sensitization in the green light region, a technique of supersensitization method which is combination techniques of various sensitizing dyes has been known as disclosed in Japanese Patent Publications No. 22884/1968, No. 4936/1968, No. 18433/1970, No. 37443/1972, No. 28293/1973, No. 25652/1973, No. 34411/1975 and No. 12375/1978; Japanese Provisional Patent Publications No. 82416/1977 and No. 16223/1977; U.S. Pat. No. 3,672,898 and the like.
However, the light-sensitive material spectrally sensitized by the above-mentioned sensitizing dyes has disadvantages that the photographic fog is likely caused, and particularly the above sensitizing method is applied to the silver halide grains containing silver iodide mentioned above, the photographic fog will occur very noticeably.
Accordingly, a first object of this invention is to provide a light-sensitive material which has a less photographic fog and a high green light sensitivity, when silver halide grains including silver iodide as a silver halide component are spectrally sensitized in a green light region.
A second object of this invention is to provide a light-sensitive material which has a less photographic fog and a high green light sensitivity, even after it has been stored at elevated temperature for a long period of time.